Chevrolet Silverado / GMC Sierra. Manual — part 1882

same and the lower gage (2) has a higher reading, the active fuel management oil
pressure relief valve is stuck in the open position or the valve lifter oil manifold filter
is plugged.

With the engine running and the lower pressure gage (2) measuring above 379 kPa (55
psi), the upper gage (1) should display no greater than 379-517 kPa (55-75 psi). If the
reading on the upper gage (1) is greater than 517 kPa (75 psi), the active fuel
management oil pressure relief valve is stuck in the closed position.

6. Repair, as required.

CYLINDER DEACTIVATION (ACTIVE FUEL MANAGEMENT) VALVE LIFTER OIL MANIF
MANIFOLD DIAGNOSIS AND TESTING

Tools Required

EN-46999 Active Fuel Management Tester. See Special Tools.

EN-46999-1 Active Fuel Management Tester Air Adapter. See Special Tools.

EN-46999-5 Active Fuel Management Tester Harness - Small Block V8. See Special
Tools.

Diagnosis and Testing

IMPORTANT:

Cylinder Deactivation (Active Fuel Management) Valve Lifter
Oil Manifold Diagnosis and Testing is applicable for RPO
LH6/LMG/LY5/LC9/L76.

A minimum shop air source of 206 kPa (30 psi) is required for
manifold testing.

A water bleed is located on the side of the EN-46999 . See
Special Tools. Occasionally, depress the valve in order to
remove excess water from the tool.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

Fig. 22: Identifying Displacement On-Demand Tester
Courtesy of GENERAL MOTORS CORP.

The manifold bench test provides a maximum 206 kPa (30 psi) of filtered shop air to the manifold
and will test each solenoid/valve for the following conditions:

Proper operation

A stuck open condition - constant air flow

A stuck closed condition - no air flow

A flow restriction within the manifold

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

1. Individually depress each of the buttons 1-4 on the EN-46999 in order to activate each of

the solenoid/valves. See Special Tools. When activating each solenoid/valve, a loud click
should be heard from the solenoid and an increased amount of air will exit the outlet ports.

Button 1 will energize the solenoid/valve 1 for engine cylinder number 1.

Button 2 will energize the solenoid/valve 2 for engine cylinder number 4.

Button 3 will energize the solenoid/valve 3 for engine cylinder number 6.

Button 4 will energize the solenoid/valve 4 for engine cylinder number 7.

Fig. 23: Valve Lifter Oil Manifold

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

Courtesy of GENERAL MOTORS CORP.

2. Do not lift the manifold assembly by the electrical lead frame.

Fig. 24: Displacement-on-Demand Tester Air Adapter
Courtesy of GENERAL MOTORS CORP.

3. Install the EN-46999-1 (1) to the manifold. See Special Tools.

4. Install 2 of the manifold bolts (2) to the EN-46999-1 . See Special Tools.

Tighten: Tighten the bolts to 25 N.m (18 lb ft).

NOTE:

Refer to Fastener Notice .

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado